JPS6375919A - Coordinate input device - Google Patents

Abstract

PURPOSE:To distinguish and judge whether the change of a measured capacitance value is due to environmental change, or the touch of a human body, by detecting the change of a capacitance when a hand is touched on a touch panel, and inputting the coordinate of a point on which the hand is touched. CONSTITUTION:The human body is touched on a non-pad type touch panel 1, and the generation of the change of the capacitance is detected, and the coordinate of a touched point is inputted to a central processing unit 3. The central processing unit 3 is equipped with a reference capacitance value setting means 31, a threshold value setting means 32, a lapse time measuring means 33, and a resetting means 34. When the processing of the central processing unit 3 is stated, the ON/OFF operations of peripheral switches 21-24 on the touch panel 1 are repeated in order, and the presence or absence of the touch of the human body is checked by the change of the capacitance. When a small width of change is generated, the capacitance measured at every prescribed time is set as a reference capacitance value before the human body is touched on the panel, by the setting means 31. In this way, it is possible to measure a touching state accurately when the change of the capacitance is unknown whether by the environmental change, or by the change of the touching state.

Description

[Detailed Description of the Invention] [Summary] When a change in capacitance is detected when a touch panel is touched with a hand, and the coordinates of the touched point are input to a central processing unit,
When a sudden change in the environment occurs and a capacitance measurement value that has changed significantly is obtained, the elapsed time is measured, and if there is no change for a long time, the capacitance measurement value is set as the reference value for the next measurement value. It is a coordinate input device.

[Industrial Field of Application] The present invention relates to a coordinate input device that detects a change in capacitance when a touch panel is touched and obtains the coordinates of a touch point.

Conventionally, when a sudden change in the environment occurs in the above-mentioned coordinate input device, the coordinate input device may operate as if it were not in contact with the human body, resulting in a decrease in the efficiency of coordinate input. It was requested that a solution be found.

[Prior Art] FIG. 4 shows a conventional coordinate input device in part in a perspective view and in a block diagram in the other part. In FIG. 4, 1 is a touch panel, 21, 22 and -24 are analog switch boards, 3' is a central processing unit, 4 is a capacitance measurement circuit, 5 is a coordinate capacitance conversion circuit, 6 is an analog switch for switching measurement sides,
10 is a glass substrate, 11 is! A TO transparent resistance film, 12 an insulating film, 13 a shield electrode, and 14 an antireflection film.

Each analog switch board has a plurality of switches arranged in parallel, and the figure shows three to four switches.

When all switches on switch boards 22 and 23 are turned off, all switches on switch boards 21 and 24 are turned on. Next, switch 22.23 is turned on and switch 21.24 is turned off. Capacitance measurement is repeated alternately. For example, when a human hand touches the panel through the insulating film 12, capacitance is added to the resistive film 11, but the capacitance added to the coordinate conversion circuit 5 is Since it is proportional to position, it is possible to detect touch and location by measuring capacitance.

The capacitance measuring circuit 4 generates a high frequency alternating current using, for example, a CR oscillator, and the timer circuit accurately measures the oscillation frequency of the oscillator to measure the capacitance. The central processing unit 3 detects the touch together with the coordinates based on the data from the capacitance measurement circuit 4, and stores them in the storage device.

[Problems to be Solved by the Invention] With the configuration shown in FIG. shows the same value as if it were in contact, and that value is retained for an abnormally long time.

In conventional capacitance measurement, when the capacitance value changes significantly from the steady state, it is assumed that the human body has touched the capacitance, so once the capacitance has changed, the measurement operation is stopped and the coordinate input process is started. Therefore, when a state change occurs due to the above-mentioned environmental conditions, it is extremely inconvenient for the coordinate input operation to stop the measurement at that point and continue it.

The purpose of the present invention is to improve the above-mentioned drawbacks, and when it is not clear whether a change due to the environment is a change due to the touch state or not,
An object of the present invention is to provide a coordinate input device that can accurately measure a touch state.

[Means for Solving the Problems] FIG. 1 is a diagram showing the basic configuration of the present invention. In FIG. 1, 1 is a touch panel, 21 to 24 are analog switch boards, 3 is a central processing unit, 4 is a capacitance measurement circuit, 5 is a coordinate capacitance conversion circuit, 6 is an analog switch for switching measurement sides, and 31 is a reference capacitance. The means for setting the value checks the capacitance measured on the touch panel l at predetermined intervals,
32 is a means for setting a threshold value, which sets a measurement threshold value obtained by adding a predetermined value to the value set in the means 31; 33 is a timer; means for measuring the elapsed time since the capacitance measured exceeds the threshold; and 34, when the elapsed time exceeds a predetermined value, sets the capacitance N measured value at that time as a new reference capacitance value. Show the means to fix it.

In the present invention, when a human body contacts the non-pad type touch panel 1,
A contact point coordinate input device that detects the occurrence of a change in capacitance and inputs the coordinates of the contact point to the central processing unit 3 has the following configuration. That is, the central processing unit 3 is provided with a reference capacity value setting means 31, a threshold value setting means 32, an elapsed time measuring means 33, and a resetting means 34.

[Operation] When the central processing unit 3 in FIG. 1 starts processing,
Turn on the peripheral switches 21 to 24 of the touch panel 1 in sequence.
It repeats the process of turning off the device, and checks whether there is any human contact by checking for changes in capacitance. At that time, even if the human body does not touch the touch panel, the measured capacitance changes slightly due to temperature, humidity, etc., so this is checked at predetermined intervals such as every 3 seconds.

When the variation range is small, the setting means 31 sets the capacitance measured at predetermined time intervals as the reference capacitance value before being touched by the human body. Since the measured capacitance value changes when the touch panel 1 is touched, the difference from the reference capacitance value is considered as a "threshold value" (fixed value) in order to judge that there is a touch when there is a large change. Therefore, the setting means 32 sets the reference capacitance value+threshold value as the measurement threshold value in the central processing unit 3. Next, while repeating the capacitance measurement, the second
As shown in the figure, when the threshold value is exceeded at time t, the central processing bag W
3 makes a tentative decision. At this time, the measurement operation is continued without being interrupted. The vertical axis in FIG. 2 is the measured capacitance value, and T'H indicates the width of the "threshold". At this time, the elapsed time measuring means 33 starts measuring time.

For example, if the measurement by the means 33 is made by a human body, it will be canceled in about 5 seconds, so the capacitance measurement in the next step [2] will normally result in a value lower than the "threshold" line. 30 years old
If the capacitance exceeds the "threshold" line even after a predetermined period of time, such as t, has passed, it is determined that the change in capacitance is not due to human contact but is due to other causes. The output of the time measuring means 33 causes the means 34 to
The capacitance measurement value at that time is reset to the new standard value. After that, when the new standard soil planting threshold line is exceeded, it is determined that the touch panel has been touched. When a capacitance change due to human contact is detected, its coordinates are calculated by the central processing unit 3 and input into the storage device 2.

[Embodiment] FIG. 3 shows an operational processing flowchart of the central processing unit 3 in the present invention. Start capacitance measurement and step (1)
Determine whether the threshold has been exceeded. If it is not exceeded and is different from the previous reference capacitance value, the reference capacitance value setting is updated. If it exceeds, in step (2), the 0 criterion for determining whether or not it is a touch by a human body is based on, for example, the magnitude of the elapsed time since the touch. When a touch is determined, coordinates are detected and calculated. If it is not a touch, it is determined in step (3) whether it has continued for a certain period of time. If this continues, re-set the reference capacitance value.

The above setting means 31 to 34 can be executed by firmware. Alternatively, it may be configured by hardware.

[Effects of the Invention] According to the present invention, it is determined from the elapsed time whether a change in the measured capacitance value is due to an environmental change or a touch by the human body. It is easy to judge. Furthermore, even if the measured capacitance value fluctuates due to environmental changes, if the fluctuation is less than the threshold value, the reference value is updated while making the determination, allowing for more accurate touch determination. Therefore, the efficiency of coordinate input can be improved.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing the principle configuration of the present invention, Fig. 2 is a diagram for explaining the operation of the present invention, Fig. 3 is an operation flowchart of the central processing unit in the present invention, Fig. 4 The figure is a diagram showing the configuration of a conventional coordinate human-powered device. 1-touch panel 21 to 24--analog switch board 3--central processing unit 4--capacitance measuring circuit 5--coordinate capacitance conversion circuit 6--analog switch for switching measurement side 31--reference capacitance setting means 32 ...-Threshold value setting means 33...Timer 34...-New standard capacity setting means

Claims (1)

[Claims] Coordinate input of a contact point that detects that a change in capacitance occurs when a non-pad type touch panel (1) is contacted, and inputs the coordinates of the contact point to a central processing unit (3). In the device, the central processing unit (3) includes means (31) for checking the measured capacitance at predetermined intervals and setting a reference capacitance value, and a measurement threshold obtained by adding a predetermined value to the set value. means (32) for setting a value; means (33) for measuring the elapsed time since the measured capacitance exceeds the threshold value; A coordinate input device comprising means (34) for resetting a measured value to a new reference capacitance value.